An air
compressor does not draw full load when it first kicks in (excluding initial
startup inrush). The current climbs as the pressure in the tank approaches

I put a Fluke clamp on to my compressor and the reality is it pulls the most
from about a fourth to half way through bringing up the tank pressure. This has
to do with the bite of air it gets to compress, When it is close to the max it
is throttled and doesn't take in much air. That is similar to a vacuum cleaner
with a plugged hose. It actually runs faster at lower current because there is
less load.